Cameras have been installed indoors or outdoors of a building for various kinds of purposes including detection of an inspection line or the position detection of a robot to be produced in a factory, and security. In some such cameras, a lens barrel can be attached thereto and detached therefrom, and various kinds of lens barrels have been proposed (for instance, see non-patent related document 1 and patent related documents 1 and 2).
FIG. 5 is a side view that shows an instance of a conventional configuration of a lens barrel configured to be attached to and detached from a camera body, a reference number B in the figure denotes a camera body, and a reference number 100 denotes the lens barrel to be attachably and detachably installed on the camera body. Such lens barrel 100 is comprised of a plurality of tube sections, 101A and 101B, configured so as to adjust a focus by relatively rotating the tube sections 101A and 101B. A reference number 102 denotes a locking screw for fixing the respective tube sections 101A and 101B so as not to shift their rotational positions.